The Center for Disease Control in Atlanta recently reported on a new species of a halophilic, lactose-fermenting Vibrio (L-plus Vibrio) which has been implicated in fatal cases of septicemia in man. Unlike the enteropathogen V. parahaemolyticus, to which it is closely related, this organism has been isolated from patients with severe tissue infections and extraintestinal lesions. Recent studies from this laboratory have shown that when the L-plus Vibrio is injected subcutaneously (s.c.) or intraperitoneally (i.p.) an extremely potent vascular permeability factor is produced which results in massive generalized edema. The acute vascular fluid loss leads to rapid and profound increases in hematocrit value, with death in experimental mice resulting in 3-6 hours from circulatory failure. The LD50 value in mice (ca. 8 times 10 to the 5th power cells injected i.p.) is two orders of magnitude less than that observed for V. parahaemolyticus. S.c. inocula in mice resulted in severe local infections, and for those surviving longer than 48 hours, tissue necrosis. These animals rapidly developed Vibrio bacteremia after injections. V. parahaemolyticus produced no morbidity or mortality when injected s.c. Injections of L-plus Vibrio into ligated ileal loops in rats and rabbits consistently proved to be lethal with a high density bacteremia resulting. Because of the potential health hazard present if the L-plus Vibrio exists at any significant level in public beach waters, the present proposal describes studies which are attempts to characterize the distribution of the L-plus Vibrio along the eastern coast of the United States. The microbiological, chemical and physical factors affecting the ecology of the organism will be investigated. Samples to be examined include water, sediment, plankton, and shellfish at each of these sites. Because of their clinical importance, the presence in these samples of two related Vibrio species, V. parahaemolyticus and V. alginolyticus, will also be monitored.